Defrost system



April 1966 w. G. WINKLER ETAL 3,247,680

DEFROST SYSTEM Filed Nov. 16, 1964 w 7277/ Glam/dew: 36 flonaldf fia anaom United States Patent 3,247,680 DEFROST SYSTEM Wynn G. Winkler and Donald F. Swanson, St. Paul,

Minn, assignors to Whirlpool Corporation, a corporation of Delaware Filed Nov. 16, 1964, Ser. No. 411,274 6 Claims. (Cl. 62-276) This invention relates to refrigeration apparatus and in particular to defrosting means for use in such refrigeration apparatus.

In one form of conventional refrigeration apparatus, wall means are provided defining a chamber to be refrigerated. The wall means further define an opening which is selectively closed by a suitable door for controlled access to the chamber. The chamber is refrigerated by suitable refrigerating means such as an evaporator coil which may be disposed selectively within the chamber of the wall means for indirectly refrigerating the chamber.

In such a refrigeration apparatus, frost tends to collect on the cold inner surface of the wall means. Thus, from time to time, the user must remove this frost as it impedes the refrigeration process in acting somewhat as an insulating layer on the wall means. The present invention comprehends an improved defrosting means which provides a number of highly desirable advantages over the known defrosting means of the art.

I Thus, a principal feature of the present invention is the provision of a refrigeration apparatus having a new and improved defrosting means.

Another feature of the invention is the provision of such a refrigeration apparatus wherein the defrosting means is arranged to be operative only when the door selectively closing the chamber is in a chamber-open position.

A further feature of the invention is the provision of such a refrigeration apparatus wherein the defrosting means is arranged to requiremanual actuation to initiate a defrost operation subsequent to the movement of the door from a chamber-closing position to the chamberopen position.

Still another feature of the invention is the provision of such a refrigeration apparatus having wall means defining a chamber, a door for selectively closing the chamber, and means for refrigerating the chamber, defrosting means comprising energizable means for heating frost deposited on the wall means in the chamber as a result of operation of the refrigerating means, means for selectively energizing the frost heating means, and means for preventing energization of the frost heating means when the door is disposed to close the chamber.

A yet further feature of the invention is the provision of such a refrigeration apparatus wherein the energization preventing means comprises a switch and actuating means operable as a resultof movement of the door to the chamber-closing position.

Still another feature of the invention is the provision of such a refrigeration apparatus wherein the switch is mounted on the door at a forward portion thereof for improved accessibility for facilitated manipulation thereof to initiate a defrosting cycle.

Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIGURE 1 is an isometric view of a refrigeration apparatus having a defrosting means embodying the invention, with portions thereof broken away to illustrate the internal construction thereof and with certain internal elements thereof being shown in broken lines;

3,247,580 Patented Apr. 26, 1966 FIGURE 2 is a transverse vertical section through the cabinet; and

FIGURE 3 is a schematic diagram illustrating the electrical control of the apparatus.

In the exemplary embodiment of the invention as disclosed in the drawing, a refrigeration apparatus generally designated 10 is shown to comprise cabinet wall means 11 defining a chamber 12. The chamber opens outwardly through the cabinet wall means at opening 13 which is selectively closable by means of a door 14. In the illustrated embodiment, the refrigeration apparatus It) comprises a chest-type freezer, although it is to be understood that any other form of refrigeration apparatus having a wall means defining a chamber to be refrigerated and a selectively closable door is within the scope of the invention.

The chamber 12 is refrigerated herein by means of an evaporator 15 comprising a plurality of coil turns wrapped about the inner liner 16 of the cabinet wall 11 so that the evaporator coil turns are effectively disposed within the wall 11 and embedded in a body of insulation 17 disposed therein.

The defrosting of the chamber, and, more specifically, the removal of frost collected on liner 16 within chamber 12 as a result of the refrigeration of chamber 12, is

effected herein by means of an electrical heater Wire 18 which is wrapped around the liner intermediate the evaporator coil turns 15 in the upper portion of the cabinet wall 11. As will be obvious to those skilled in the art, other suitable conventional defrost means may be employed within the scope of the invention for effecting the removal of the frost collected in the liner 16.

The refrigeration apparatus includes herein a conven tional compressor 19 which is disposed in an apparatus space 20 defined by an offset portion 21 of the wall 11 at the lower rear of the cabinet. A drain duct 22 is provided through the wall 11 leading downwardly from the bottom of the chamber 12 through the wall and into a suitable collecting pan 23 at the bottom of apparatus space 20.

The control of the defrosting operation in apparatus 10 is effected by means of a snap switch 24 which, as shown in FIGURE 3, is connected in series with the heater wire 18 and a suitable defrost thermostat 25 across a pair of power supply leads L and L which may be connected to a conventional power supply source by means of a conventional outlet plug 26. The switch 24 is operated by an actuator 27 which is arranged to provide a novel control'of the switch preventing energization of the defrost heater 18 when the door 14 is in a chamber-closing position. While the switch 24 may be selectively mounted either on the cabinet wall 11 or the door 14, in the illustrated embodiment the switch is mounted on the door 14, with the actuator 27 extending downwardly therefrom to engage a cabinet wall portion 28 for throwing the switch from theheater-energizing, or on position to a heater de-energizing, or off, position when the door 14 is swung downwardly, as on hinges 29, to the chamber-closing position shown in FIGURE 2.

More specifically, as shown in FIGURE 3, the switch 24 has a movable switch member 30 connected to a power supply lead L and a first fixed contact 31 connected to the heater 18. The switch is arranged so that it is necessary to manually operate actuator 27 to move the contact 30 into engagement with fixed Contact 31 to initiate a defrost operation. As the switch is accessible only when the cabinet door 14 is in the open position, the

chamber 12 is automatically open-to-atmosphere when the.

user initiates the defrost operation. If at any time the user moves the door 14 to the closed position, i.e. closing opening 13 as shown in FIGURE 2, the actuator 27 engages wall portion 28 and throws switch 30 from engagement with fixed contact 31 and into engagement with a second fixed contact 32. The second fixed contact 32 is connected through a conventional magnetic starter relay 33 to a two-winding compressor motor 34 which in turn is connected to power supply lead L through a series connection of an overload relay 35 and a chamber-temperature sensing thermostat 36. If desired, the apparatus 14 may include a lamp 37 connected in series with a suitable position-responsive switch 3%, herein a conventional mercury switch, across power supply leads L and L for illuminating the chamber 12 whenever the door 14 is swung to the open position of FIGURE 1.

Thus, in operation, refrigeration apparatus 161 normally functions to refrigerate chamber 12 to a preselected low temperature under the control of thermostat 36 as long as door 14 is arranged in the chamber-closing position of FIGURE 2. Whenever the door 14 is raised, as by manipulation of handle 39 by the user to pivot the door to a chamber-open position as shown in FIGURE 1, the switch 24 is madeaccessible to the user for actuation as desired. More specifically, where the user is merely placing articles in the chamber 12 or removing articles therefrom no actuation of the switch 24 is effected. However, when the user determines that a defrosting operation should be effected, he merely pulls the actuating member 27 downwardly to throw the switch 24 to the defrost heater-energizing position. As long as the door 14 is maintained in the chamber-open position of FIG- URE 1, the switch 24 will remain in the heater-energizing position wherein the defrost heater wire 18 is electrically energized under the control of the defrost thermostat 25. Thus, heating of the liner 116 is continued until the defrost thermostat senses the removal of the frost from the liner whereupon the energization of the heater wire 18 is automatically discontinued, even though the switch 24 is maintained in the heater-energizing position.

All melt formed by the melting of the frost on the liner 16 during the defrost Operation runs down through the discharge duct 22 into pan 23 for subsequent disposal by evaporation into the ambient atmosphere during subsequent operation of the compressor v19 in the apparatus space 21).

Upon completion of the defrost operation, the user merely closes the door 14 whereupon the switch 24 is thrown from the defrost heater-energizing position to the compressor-energizing position wherein the movable contact 30 engages fixed contact 32. Subsequent opening of the door 14 has no eifect on the switch 24 until such time as when the user once again manually operates the actuator 27 for initiating a subsequent defrost operation. Further, opening and closing of the door 14 has no effect on the compressor circuit and thus the compressor may operate in the normal refrigeration cycle under the control of the thermostat 36.

While we have shown and described one embodiment of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. In a refrigeration apparatus having wall means defining a chamber to be refrigerated, a door for selectively closing said chamber to provide controlled access to said chamber as for placing therein and removing therefrom articles to be refrigerated therein, and means for refrigerating said chamber, defrosting means comprising:

energizable means for heating frost deposited on said wall means in said chamber as a result of operation of said refrigerating means;

means for selectively energizing said frost heating means; and

means precluding energization of said frost heating means whenever said door is disposed to close said chamber while permitting selective energization or deenergization of the frost heating means when the door is disposed to open said chamber.

2. The referigeration apparatus of claim 1 wherein said frost heating means comprises an electrically heatable element extending in said wall means.

3. The refrigeration apparatus of claim 1 wherein said frost heating means comprises an electrically heatable element extending in said wall means, said energization precluding means is carried by said door, and said energizing means includes a flexible connection between said energization precluding means on said door and said element in said wall means.

4. The refrigeration apparatus of claim 1 wherein said energizing means includes a manually operable switch connected to said frost heating means and having an on position and a off position and requiring manual operation of the switch to throw the switch to the on position from the off position, and said energization precluding means includes means for throwing said switch to said off position as a result of movement of the door to a chamber-closing disposition.

5. The refrigeration apparatus of claim 4 wherein said switch is mounted on a portion of the door arranged to be spaced substantially from the wall means when the door is in a chamber-open position to provide facilitated manual operation of the switch.

6. The refrigeration apparatus of claim 1 wherein said energizing means includes means requiring manual operation thereof to initiate energization of the heating means and disposed to be accessible for such manual operation only when the door to the refrigerated chamber is arranged to open the chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,124,268 7/1938 Williams 62276 2,234,474 3/1941 Higham 62276 2,426,578 8/1947 Tobey 62-272 2,483,842 10/1949 Philipp 62444 WILLIAM J. WYE, Primary Examiner. 

1. IN A REFRIGERATION APPPARATUS HAVING WALL MEANS DEFINING A CHAMBER TO BE REFRIGERATED, A DOOR FOR SELECTIVELY CLOSING SAID CHAMBER TO PROVIDE CONTROLLED ACCESS TO SAID CHAMBER AS FOR PLACING THEREIN AND REMOVING THEREFROM ARTICLES TO BE REFRIGERATED THEREIN, AND MEANS FOR REFRIGERATING SAID CHAMBER, DEFROSTING MEANSR COMPRISING: ENERGIZABLE MEANS FOR HEATING FROST DEPOSITED ON SAID WALL MEANS IN SAID CHAMBER AS A RESULT OF OPERATION OF SAID REFRIGERATING MEANS; MEANS FOR SELECTIVELY ENERGIZING SAID FROST HEATING MEANS; AND MEANS PRECLUDING ENERGIZING OF SAID FROST HEATING MEANS WHENEVER SAID DOOR IS DISPOSED TO CLOSE SAID CHAMBER WHILE PERMITTING SELECTIVE ENERGIZATION OR DEENERGIZATION OF THE FROST HEATING MEANS WHEN THE DOOR IS DISPOSED TO OPEN SAID CHAMBER. 